Automatic telephone switch



F. MERK March 15; 1932.

AUTOMATIC TELEPHONE SWITCH Filed May 25, 1929 7 Sheets-Sheet March 15, 1932. Y F. MERK 1,849,986

AUTOMATIC TELEPHONE SWITCH V Filed May 25, 1929 7 Sheets-Sheet 2 H93 fig. 4; 1 5:

in vemz ar fitter e315.

March 15, 1932. F. MERK 1,849,986

AUTOMATIC TELEPHONE SWITCH Filed May 25, 1929 7 Sheets-Sheet 5 March 15, 1932. MERK 4 1,849,986

AUTOMATIC TELEPHONE SWITCH Filed May 25, 1929 7 Sheets-Sheet 6 Event F. MERK March 15, 1932.

AUTOMAT IC TELEPHONE SWI TCH Filed May 25, 1929 '7 Sheets-Sheet 7 L venior' y Mam Patented Mar. 1932 NT OFFICE.

FRIEDRICH MERE, OF FRANKIORT-ON-THE-MAIN, GERMANY anromrrc TELEPHONE swrrcn Application filed May 25, 1929, Serial No. 365,950, and in Germany May 26, 1928.

- The invention relates to selectors with a switching memberwhieh is driven by a con- 'stantly acting force and of which the operation is controlled through an intermittently 5 acting device, by means of a pawl mechanism. Such selectors are well-known for step-by-step adjustment in several forms of construction Generally, the switch member is driven by a spring or by its own weight, and is controlled by a pawl mechanism-set into oscillation by an electromagnet, which, at each current impulse sent through the electromagnet, executes a to-and-fro movement which allows the switching member 'to move forward by one-switchingste'p." I The. invention-has for its object an improvement of the abovefinentioned selectorsby permitting, whilst still retaining the stepby-step adjustment, the executing of a uni form movement (sliding movement) by the I switching member. This 'dual. adjustability deserves special consideration because, when the selector operates .as a line finder, a sliding movement of the-switching member is preferably to a'stepby-step movement, whilst the step-by-step operation is, in any case, the operating form best suited for numerical selection. I

The invention is distinguished from wellown proposals, which likewise-may be operated, as desired, witha stepby-step or uniform movement of the selector switching member, by thespecial simplicity of the cony the use of. the controlling struction which, I j devlcelindicated besides pawl mechanism, is

- y applicable to both types of use. I

The sliding movement of the switching. member; according to the invention, is accomplished bythe frequency and phase of the impulsestransmitted to ber'being so adjusted with reference to the speedof the switching member that 'the pawl mechanism, set into'oscillation by the control member, constantly avoids engagement with the switching member up to the moment of its stopping and thereby makes free the path of movement to the switching member for any length of switching step. -Acomplete adjustment of the frequency and phase of the impulses of the control member ,to' the scribed, both selections the controlling memspeedof the switching member is obtained, inany case, by making the same dependent upon the switching member itself. The electromagnet, normally provided as the controlling device for the step-by-step operation, is quite suitable for executing the sliding operation. The transferring from the step-by-step operv ation to the sliding operation necessitates, in this case, merely transferring the conductors of the electromagiiet from the'circuit for the numerical current impulse reception, to alocal circuit withan interrupter controlled by the switching memberl' The advantage of thedoublekind of adj ustability of the switching member becomes 65 important particularly in the case of selectors adapted to perform difi'erent selecting operations, since, in this case, according to the manner of use of the selectors, either all'the selectors or any individual ones may be supplied with ,step-by-step orjsliding operation, as required. In the following description of a constructional example of the invention, it-is assumed that the selectonis'for'twofold selection (group andindividual line se; lection). Moreover, in the example. de-

are in the same directhe arrangement for made in sueh'a mantion of movement and the group selection is ner that both adjusting movements ofthe p selector are controlled with one single controlling and pawl device. v

The generalimportance of the invention consists in that it balances th e contrast between the modern existing types of main selectors with step-by-step and machine. drive. Hitherto, there existed i the conception that the step-by-step operation only'comes into the question for lightly constructed selectors, in. contradistinction to which selectors with a heavy switching member-must havea machine drive. Thisvie w cannotrbe held against a se'ector arrangement .Whichcombines the step-by-step and sliding operation with one another'in a simple and suitable manner for gnyldesirable use. If, as in the following example for explaining the' invention, care is taken that, with thegroup and individual line selection always small switching-steps are used, then the limitation of-the step-by step operation to the numerical selection makes possible a multiple decrease of the natural speed of the switchingmember in relation to known selectors with step-bystep drive,-and thus a considerable increase in weight of the switching member without disadvantage to its operation is permissible.

This theory is better explained in the.fol-

- lowing with the aid of several diagrams. In

order, however, to prove the success of the method, it may be said that on'selectors constructed according to the invention, with large switching output and steady working,

a weight of 1 kilogram and more per switching member-is permissible. Thus the invention is applicable to the use ot the selectors with large contact fields particularly in the economical'form of bar selectors with flat bank contact groups as were hitherto reserved for the machine'drive, dispensing with the hitherto usual impulse storing register.

In theidrawings Fig. 1 represents the front view of a complete selector for 100 lines.

Fig. 2 represents a section of the switch on the line 22 of Fig. '1.

Figs. 3-5 show the switching member in ment of the changeover contacts controlled y the selector.

Fig. 18 shows a special construction of the driving mechanism.

Referring to Figs. 1 and 2, the selector consists of a switching member 100 extending transversely across the ten groups of bank contacts 1 -10, a driving mechanism 200 and three sets of contact springs e, f, g. The hori- I zontallyextending bank contact groups 1- 10 are located at equal distances above one another and form the flat contact bank composed, in well-known .manner, of'groups of metal contacts and insulation, forming a plurality of similar switches. Each bank contact group contains the contacts of a group of ten lines, each comprising three contacts.

The multiple contacts of the individual lines are arranged in three rows 11-13 extending in the direction of movement of the switching member. The numbering of the bank contact groups of-lines proceeds, in the present case, from the bottom to the-top; and the numbering of the lines of each group from the top to the bottom. The contacts of line No. 23, for example, are located in the third position from the top in-the second bank contact group from the bottom.

-1,s49,ese

Above the contact bank is provided a bar 14 with three current lead bars 15 for every the switching member 100. I The numbering of brush sets corresponds to that of the bank contact groups and as usual all the brushes a are connected with one another in multiple, and also all t he brushes 1) and '0 respectively. 'Whenithe switch is used as a call finder, as shown in the drawings, there is provided below'the contact bank a special extra bank contact group 16, which contains the contacts of ten' tens lines for determining, in the case of line finders, the group in which the calling subscribersline is located. The ten in: dividual contacts 17 of this bank contact group form a single row of contacts located above one another, and have a current introducing bar 18 extending adjacent thereto.

The bank contact groups 1-.1O and 16, as well as the bars 14 with the current leads 15, are positioned in av frame 19 which also serves as a support for the remaining parts of the switch. The frame allows of the correct assembling of all parts of the switch to vthree brushes a, 'b, c of the brush set 104 of form a complete unit independent of theother devices, relays, and so on with which the switches are subsequently connected by connections on the frame.

The switching member representedin Figs.r3, 4 and 5 is composed of two parts,

namely a brush carrier and a brush se-.

lector 106. Thebrush carrier 105 is located on four bolts 20 at thetop and the bottom of the switch frame 19 (Fig. 2), and consists, of two angle irons 107 between which the brush sets 104 are secured so that they may be readily interchanged at definite distances apart.

For each bank contact group 110, a brush set 104, comprising three flat adjacent brushes for wiping over the contact rows 11, 12 and13 embedded in insulating material 108, is fixed to the brush carrier. In addition, at the .top of the brush carrier are provided three spring wipers 109 (Fig. 2), for wiping over the three abovementicned current lead bars 15. All the corresponding brushes 0, b, 0 of the brush sets 104 are electrically connected to-'.

gether by wires 110 and also to the corresponding wiper 109 whereby all the brushes Y a are'connected with the-first bar 15, andcorrespondingly all the b and c brushes each with one of the other bars 15. If the switch is employed as a line finder, the brush carrier 105 carries at its lower end an extra two-part brush set 111 whose brushes d and 113 are tens contacts 17 (Fig. 1) of the bank contact group 16, whilst the brush 113 always contacts withthe'current lead bar 18. j

Whilst the brushes ofthe brush set 111 7 always} rest on their associated contacts, the

brush s'ets 104 are usually out of engagement .tatably mounted upon the anglebars 107,

with their associated contacts, that is, the

brushes (1, b, a rest, in; the normal position, contacts, each resting preferably triangular control which individual brush set 104 shall make contact with its associated contacts. In the case of the-triangular rod, for example, this is effected by rotating it through 60 so that its edge restsagainstthe springs :a, b, c

of the desired brush set and makes them pro ject from thespacefbetween the two angle plates 107 to engage with "the desired bank contact group. (see middle'brush set of Figs.

3v and 4). The rotation-0f the prisms is a small'toothed wheel 115 arranged at the end of each prism (in the case of the triangular prism it has three teeth) and by-pins 116 secured on the brush selector 106.- The pins 116 are so displaced with refere'nce-to the prisms 114 that on the displace ment of the brush carrier 105 with reference to the brushselector 106, each toothed wheel 115 of a prism successively engages with its individual operating pin 116 whereby the switching step through 120, whereby it switching steps so-thatthe prism of the sec-' prisms are individually rotated in succession. In the. case of'the. switch shown the brush carrier 105. moves downwards in both se1ect- .ing operations, whilst the. brush selector.106 7 .is held during the-first selecting operation and moves with the brush carrier during the second selecting operation. When the brush carrier 105 moves downwards withthe brush 4 selector 106 fixed, the prism 114 of the lowest brush set 104, is rotated step-by-step when it meets itspassociated pin 116;- in the first switching step through and in a second reaches a position corresponding to its initial position, whilst, by this second switching step, the prism of the .brush set next above carries out its first rotary step. In Figs. 3 and 4, the brush carrier 105 has. moved two 0nd brush set has been rotated through 60 and-is thereby located in the operative position. The-prism'of the first brush'set has, on the other'hand, been rotated through 120 and back into its normal position, it having been set in the operative position by the first switching step. Should the brush carrier be lowered by a further switching stop, the third 7 brush set will be locatedin the operative position, and the second brush set will have'been returned to'itsnormal position.

progressive changing In order to effect this over ofthe brush set, the successive distance between pins 116 onthe'brush selector 106 which cooperates with the toothed wheels by one switchingstep. tances are indicated on the right of by the reference steps.

The changing over of a brush set 104, de-- .carrier 105 when it is front of the first a particular manner.

characters 001,012 re indicating thenumber of the index fi their associated bank'contact groups 110, in

successivedistancesbetweenthebrushes,starting from the first brush, increase successively by one switching step. The reference characters m2, m3 011. shown on the left of Fig? 5 indicate, by spacing distances in switching steps of the brush sets from the actual first contact of each bank contact group. i

. The above described brush selector arrangement also ensures the returning of the parts of the switch into their initial position when the'switch is-released after having established-a talking connection, since on the raising of the brush carrier 105 at the termination of the connection, the pins 1160f the brush selector 106 rotate'the prisms 114 in the reverse sequence and direction. In order that the brushes a, b, c which are inclined obliquely with. reference to the contacts of the bank contact groups 110 do not catch on these contacts, their operation during this reverse movement is again effected, as is seen later, outside the contact groups and below the 1 last contact of each bank contact group.

their index numbers, the

Also in this case, the' l The total length of dropof the brush carii rler amounts to 22 switching steps, of which ten are employed for the selection of the bank contact group, and a further ten for the. selection of. the individual line in the group; whilst the two further steps are employed for initiating the return of the switch to normal. The length of drop of the brush selector 106 amounts only to half this number of switching steps, since, as mentioned, it moves with the brush carrier only during the second selecting operation. On. the terminationof a connection,- the brush carrier and brush selector continue the falling'movement until the brushfselector reaches its lowest position, The brush selector has then travelled eleven steps in. all..'- .When this position is reached the restoration of the parts of the switch to normal begins; first only the brush carrier is raised, bythe same distance which it. travelled alone at first in selecting the f I group, whereupon it engages with and car-' ries the brush'selector with it, both' parts together being finally restored to the initial position.

-' During these various movements of the brush carrier-105 and the brush selector 106,

the contactspring sets e, f,g (Fig.1) are operated. These contact spring sets are secured to a frame 21 which engages with the upper end of the switching member 100. Their operation by the switching member will be described with reference to Fig. 17. The contact spring set a is operated by a projection 117 secured to one of the angle bars 107, and, in the normal position, stands between the two springs 22. If the brushcarrier falls during the first selecting operation, then the projection 117 leaves, on the first step, the position indicated, and the contacts of the spring set e are changed over. The contact springs set f is operated in similar manner by a projection 118 which is secured to the brush selector 106 and which, in the normal position, stands between the two springs 23. The operation of contact spring 9 is effected by a projection 24 which is securedto the endof a lever 26, rotatably mounted on the shaft 25. The lever 26 ordinarily stands in the position shown, so that the projection 24 presses the springs 27 away from one another. Not until the brush selector 106 is brought into its lowest position after the termination of a connection, does the v pin 112 secured on the brush selector 106 ensets,

gage the top of the lever 26 and move it into the position indicated by dotted lines,

whereby the projection 24 is ejected from between the springs 27. On the restoration of the switch to normal, the brush selector 106, duringits last upward step and by means of the projection 118, engages with the underside of the lever 26 and rotates the latter back into the normal position. Thus the contact after their first operation, are not operated again until the brush carrier 105 and the brush selector 106 are returned to the normal position. The driving mechanism 200 represented in Figs. 6 to 9 controls the movement of the switching member 100, that is, the dropping and raising of the brush car- I rier 105 and the brush selector 106. The driving apparatus is independently interchangeable and is secured to the switch frame 19 below the switching member.

To the front of a rectangular longitudinal base plate 201 is secured, by means of a bracket 202, a round guide-rod 203. In the upper'half of the base plate 201, behind the guiderod 203, a longitudinal opening 204 is located; Between the opening 204 and the guide rod 203 capable ofbeing moved,-is arranged a flat toothed rack 205, guided at its upper end by means of a crosspiece 206 ridingin the opening 204 in the base plate,

and

, at its lower endby. means of a bent over limb 207, embracing the guide rod 203. 'Onthe back part of the crosspiece 206 of the rack 205, rests ,the stretcher 119 (Fig. 3) extending between the members 107 of the brush carrier 105. Thus the movement of the brush carrier 105 is controlled bythe rack 205. a

The guide rod 203 als guides a U-shaped -rear a projec member 208.- The lower limb 209 'of this member is, in the normal position as shown in Fig. 7, at a distance of eleven switching steps like eleven times the pitch of rack 205 below the limb 207 of the rack 205. The upper limb of this member carries towards the ion 210 which engages in a slot 120 formed n' the brush selector 106. Thus the member 208 controls the movement of the 'brush selector 106.

The two edges of the-rack 205 have "of different form, formed thereon, the teeth of the driving mechanism (the drawings show the mechanisms in this position) the locking 'pawl 215 is at a distance of one switching stepfrom the lowest locking tooth 212 and bears on the untoothed part of the rack. An

electromagnet N secured to the base plate 201 engages, on energization, by its armature 217, (Fig. 8) the upper arm 214 of the locking pawl and thus holds it, against the action of the leaf spring 216, out of engagement with the locking teeth 212. When the locking pawl 215 is in this position, the rack 205 can move downwards, independent of the member 208 which is Tetained in its initial position by means of'the spiral spring 218 surrounding the guide rod 203. The spring 218 is so highdriving mechanism that, on the independent downward movement of the rack 205, the decreased effort exerted, is always sufiicient to hold the upper limb of the member 208 in position. 1

As soon as the armature 217 liberates the 'ly compressed in the normal position of the lever 214 on deenergization of the electromagnet N, and the locking pawl 215 is forced into .engagement with the locking teeth 212 under the action of the leaf spring 216,- the action of the spring'218 is stopped and the member 208 is positively carried along by the rack 205. Thebrush carrier 105 resting on the crosspieee 206 of the rack 205, then moves the brush selector 106 simultaneously with it,

coupled by the projection 210 of the member 208.

If,.on account of a failure of the electromagnet N, the leakin pawl 215 does not engage the locking teeth 212, by the tenth switching step, the guide limb 207 of the rack 205 engages, on the eleventh step, with the lower limb 209 of the member 208 and carries this member along with it, providing the movement necessary to reach the end posiis regulated'by a locking device controlled by the base The? magnet is secured to the .special base plate; 220 mounted onfour pillars 219, secured to the base plate 201, infront of the guide rod 203. shaft 222'is rotatablyjmounted between the special base'plate 220 and a bridgememher 221 arranged parallel to and some distance from 'plate220, and is provided .with a I drivingwheel' 223, a locking wheel 224 and a cooperatinglwheel 225. The driving Wheel 223 engages with the driving teeth 2110f the rack 205 and transmits the weight of the switching member resting on the rack, together with the pressure exerted by the helical spring 218, to the locking wheel 224. This locking wheel cooperates with an escapement pawl 227 secured to the armature'226 of the release magnet M and thus only permits the rack 205 to move downwards in accordance with the oscillations of the cscapement pawl, caused b the release magnet M. The release magnet on attraction and release of its armature '226, causes the escapement pawl 227 to be alternately moved into releasing wheel 224, and the gear contact opening-and a con-tact switch 2.

and locking positions, so that the locking wheel 224, on each excitation anddeenergization of the electromagnet, rotates through one tooth division. The teeth of the locking ratio between the driving wheel 223 and the driving teeth 211 of the rack 205, are so selected that each ro- "tationof the locking wheel 224 through one tooth division advances the rack 205 and the brush carrier 105 by one switching step. Thus each current impulse acting on the re lease magnet M advances the brush carrier by one switching step.

The cooperatingwheel 225 transmits this movement to a pinion 228, on whose shaft 229 issecured the interrupter disc 230. This I interrupter disc 230, during its rotation, en-- ters between the lugs 232 of th'e semi-circular contact spring 2'. The gear ratio between the pinion 228 and the cooperating wheel 225 is such that every switching step causes a closing of the (The interrupter disc 230 is so adjusted on the shaft 229 that in the normal I Y isdeenergized and permits the lockingwheel GI) position of the driving mechanism the contact z is closed. The contact is, however,

opened as soon as arelease magnet M allows the locking wheel 224 to partially rotate, owing to'the attraction of its armature, but again temporarily closed when the magnet to complete the switching step.

The interrupting contact 1' regulates independently of the movement of the switching member, the transmission of 4 current impulses tothe release magnet M for producing a uniform mot onof the swltchlng memb e'r.

If, for example, the magnet M is connected in welltail, in a circuit extending through the contactz', then it is excited through this contact,

fore this tooth hits against the left arm of the escapement pawl 227, however, the disc 230, by opening the contact z', breaks the circuit, so that the armature226 falls back under the action of the spring 250, removes the left arm of the escapement pawl 227 from in front of the tooth and moves the right arm -'1nto the locking position. Before, however,

the tooth meets the right arm of the escapement pawl, the contact 2' is again closed by the further rotation of the interrupterdisc 230, whereby the magnet M responds again and the operations are repeated. The transmission of current impulses to the release magnet M, thus controlled by the switching member, causes the escapement pawl to swing with such 'a period that it continuously avoids engaging with the teeth of the. locking wheel 224. Thus the locking wheel can rotate continuously, unimpeded,-so that the :witching member moveswith uniform moion. i

For restoring the switching member to normal, an air driven device (Figs. 8 and 9) arranged on the back of the base plate 201, is employed, and consists of a cylinder 233 with a piston 234 and a valve 235. ,The piston rod 236 connects with the guide crosspiece 206 of the rack 205, upon which the stretcher 119 of the switching member rests. The valve 235 connects the lower cylinder space either by the passage 237- with the atmosphere, or by the passage 238 with a compressed air pipe 239. By means of the valve pressure exerted by the switchfront of the base .the driving mechanism.

own manner, explained later in de- The operaon the front of the base plate 201, and moves the same downwards. is released by the projection 244 on the slide, whereby the compressed air in the pipe 239 shifts the valve 235 towards the right and flows into the lower cylinder chamber. Since the piston rod 236 and the rack 205 are connected, the compressed air flowing in lifts the rack 205, together with the brush car- The leaf spring 241 rier 105. v The member 208, together with the brush selector 106 of the switching memher which is coupled with it, remains, however, at first, in its lowermost position, because it is held in this position by a locking pawl 246 engaging with a groove 245 formed therein. When the rack 205 has been raised so far that it'assumes the same position relative to the member 208 as in the normal position, that is when the guide limb 207 of the rack 205 is at a distance of eleven steps from the, lower limb 209 ofthe member, a projection 247 mounted on the --limb 207, presses .against the projection 248 on the locking pawl246, thereby moving the latter out-of' the groove 245,. and releasing the member 208 which then moves with the' rack 205 into the initial position, On approaching the initial position, the lower limb 209 of thestored to the normal position.

During the downward movement of the rack 205, the piston 234 slows down the drop-- ping speed since. in moving; it draws in air in the upper cylinder chamber through the small opening 251 and at the same time forces the air present in the lower cylinder chamber out through the relatively small valve passage 237. A suitable form of valve might in some instances-be advantageously placed in said air inlet opening 251 for controlling the intake therethrough so as to'regulate the rate of falling movement of the piston in the cylinder, although such is not here shown in this case as it is not required and would be an obvious addition.

The general method of operating the selector I For selecting the desired bank contact group, the electromagnet M receives current impulses which cause the escapement pawl 227 to release the locking wheel 224, and thus 'also the rack 205 on which the .brush carrier 105 rests. The movementof the brush carrier and the rack is efiected by the weightof the carrier/in'steps, or uniformly, according as the current impulses are generated by a numerical switch or the interrupter i. As soon as the brush carrier leaves the normal position, the set of contact springs e is operated. During this first movement of the selector, the magnet N is-energized and holds the locking pawl 215 out of engagement with the-locking teeth 212 of the rack 205, The member 208, and the brush selector 106 coupled with it by the projection 210, remain,

therefore, under the influence of the spring 218, in the normal position. -Consequently secured to it, moves relatively to thebrush selector 106. The small toothed wheels. 115

of the prisms 114 of the individual brush sets 104, engage in succession with'the pins 116 on the stationary brush selector 106. With each switching step, one prism'after the other,

starting from the lowest brush set 104, is

rotated, the brush sets being successively changed over into the operative position and, on the next switching step, being further r0 tated to the normal position.

the brush carrier 105, with the brush sets 104 When the desired bank contact group is se lected, that is, when its corresponding brush set is in the operative position, the brushes (1,6,0 of this brush set then stand one switch ingstep in front of the first contact, of the i I corresponding bank contact group. The magnet N is now-deenergized and releases the locking pawl 215. which falls into the teeth I 212 and couples the member 208- with the rack 205; During the further movement of the brush -carrier 105, the brushiselector 106 is carried along with it and thereby the set of contact springs f is operated. The'brushes of the operative brush set wipe over the contacts of the selected bank contact group. As

soon asthe desired individual line is reached,

the movement of the brush carrier is stopped by the stopping of the escapement pawl 227 tion, new current impulses aresent through the magnet M so that the brush carrier 105 at final deenergizatiorrof the ele'ctromagnet To restore the selector to the normal posi-.

and the brush selector 106' continue moving until the brush selector 106 has reached its lowest position. In this position the contact spring set 9 is operated by pill 112 and lever 26 (Fig. 17) and the circuitfor the magnet -M interrupted. The lower limb 209 of the member 208 moves the slide 243 which lifts the spring 241 and releases the valve 235. Compressed air then flows into the cylinder 233 from the supply pipe239 and moyes the piston 234, together with the rack-205 and the brush carrier 105, upwards. The brush selector'106. and the member 208 are, at first, held by the locking pawl 246. Consequently the small toothed wheels 115 of the prisms,

which had been changed over in the group i selecting operation, successively engage the pins 116 on the brush selector 106, and are I rotated in reverse direction. This operation is performed upon each'su ccessive brush set as each successively approaches the lowest contact of-its associated bank contact group. When the lowest brush set,.whi'ch is the last to be operated, is changed over, the limb207 of the rack 205 releases the locking pawl 246 fro the member 208, so that the brush selec or 106 and the brush carrier 105 return together to the normal position. The contact sets 6, f, g are then restored to their nor- 1 ing member in motion, the other half being are. in this' case,

241 again closes the valve235.

Figs. 10 to 14 represent different speed diagrams for the switching member, which show the diminution in the speed of the-switch ingmember itself, permissible in switches according to the invention,. whilst still ii1-- creasing the operatingspeed of the switch. On the abscissee is plotted the-time andon the ordinates the natural member.

with electromagnetic'step by-step drive, used as a line linden. The maximum practical stepping speed amounts to about '50 steps per second, since for each attraction and release of the armature, about 1/ 50 of a second is required. In this case during only half the time of each switching step is the switch- "lost by the release of the armature to overstep the next'notch-between the individual" switch movements. The movements inthemselves rapidly accelerate and the speed curve is therefore very steep.

Fig. 11 shows the condition for the case in which the'switching member traverses the same switching distance with uniform speed, for example, in a braked falling movement inaccordance with the above description. The initial oblique slope of the curve "corresponds to the starting. The figures annexed underneath indicate, as in the case of Fig. 10, the individual switching steps, and the times for traversing these successive steps may be read from the diagram. The equality of the sections and the whole switching distance appears from the comparison of the corresponding graphs of Figs. 10 and 11. A comparison shows that in Fig. 10 the maximum speed of the switching member with each switching step is 4% times as great as in Fig. 11, although the operating time in the latter case is shorter by a time period.

Fig. 12 is a speed diagram of a selector with electromagnetic step-by-step drive, used as a numerical selector. The usual number of steps amounts, in this case, only to 10 steps per second. The difference with respect to Fig. 10 is expressed merely by the inact ve periods between the switch movements,'wh1ch periods of motion of the switching member. These periods of motion of the switching member last exactly as long as in Fig. 10, because, with selectors with exclusive elec tromagnetic step-by step drive, the natural speed of the switching member must be adapted to the quickest connecting speed (Fig. 10) and is invariable. The speed attained is obviously unnecessarily large for;

- the purpose of a numerical selection.

Fig. 13 shows, in contra-distinction to Fig.

12, the conditions for the case in which a sewith the speed of the setting when controlled by means of the are less dependent upon the accuracy of the nine times as long as the lector according to the invention iso rated by numerical current impulses. In t is case the maximum speed of'the switching member with each switching step is, in comparison revious case, 5 to 6 times'smaller, because, rstly, the .escapement divides each switchingstepintotwo half steps, and sec ondly the drive is effected by a continuously acting force (gravig) which produces a v uniformly accelerated otion. Thfi shaded surfaces of every two half steps ig. 13) cor- V o respond toeach shaded surface of Fig. 12. '10 is a speed diagram of'a selector he. movements .of the switching member escapement,

numerical selecting current impulses than in the case'of electromagnetic stepping. Short current impulses suifice to operate the switching member according. to Fig-13. Even with quite short current impulses, no failure takes place since in this case the two half steps-are combined into one step according to Fig. 14. In this case the air piston brakes the speed towards theend of the motion and holds it constant at the highest desired speed. This braking is permissible in numerical selection since the time switching steps are still sufficiently large to ensure perfect operation.

The limitation of the maximum natural speed of the switching member to a considerable lower value than stepping, permits the switching member and other moving parts to be more massively constructed since the kinetic energy liberated on the stopping of these members is only directly proportioned to the mass of the members whereas it is proportional to the s uare of their speed. The switching mem er can therefore be strongly constructed and rigid in itself, thereby eliminating several members, which were previously necessary to guide the switching member along the contact bank. The guiding is efiected in the constructional example shown (Fig. 1)- merel by the bolts 20 at the top and bottom end 0 the contact bank. Any frictional resistance curring during the motion of the switching member may be neglected on account ofthe large force exerted in driving the switching member by its own weight. This simplification of the guiding arrangements and the fact that no limitation in the weight of the switching member is necessary, makes the construction of the selector cheaper and more economical in use than hitherto.

The method of operation of the switching acting as a call finder, group selector and connector will now be explained with reference to the following circuit diagrams, Figs. 15 and 16, which show an exchange of 1000 subscribers. Each subscribers form a group with about ten line finders, group selectors and connectors associated therewith. In Fig. 15, S1 shows the switch acting as a line with electromagnetic guiding ferred. by a distributor V in the exchangev finder, S2 as a group selector and S3 (Fig. 16)

as a connector with the necessary control relays.

If a subscriber, for example, No, 123, Wishes to call another subscriber, say No. 321, the method of operation is as follows.

The call of the subscriber No. 123 is trans- (Fig. 15) to a free line finder S1 of the first one hundred group. The brush carrier of this line finder is released and moves downwards at a uniform speed whilst the brush selector is at first held. By this meansthe tens group in which the calling subscribers line is located, is selected. On testing every tens group, the corresponding brush set of the second group,

ing the uninterrupted continuous so to the group selector S2 associated with the line finder S1, and the distributor V, up till then connected with the line finder, is released.

The operation of the group selector is dif-.

ferent insofar as, during the group selection, the brush carrier is oved downwards with a step-by-step instea ofuniform motion. In accordance with the three current impulses sent out by the subscriber, the brush carrier moves downwards, again free from the brush selector, by" three switching steps. Thebrush selectoris then released for the associated movement and-since, at the same time, the release magnet of the group selector is connected, by thecurrent impulse relay, to the local circuit of the automatic interrupter, the brush carrier and brush selector move downwards at a uniform speed, the third brush set wiping over the lines leading to the connectors of the selected third hundred group. On finding a. line leading to a free connector, the brush carrier is stopped and the calling subscriber is extended to this particular connector. I

The method of operation of the connector differs from those of the previous cases insofar as the brush carrier-is moved step-bystep inthe selection of tens and-units corresponding to the numerical current impulses 2and l sent by the calling subscriber. Since, as previously, the brush selector only moves during the second selecting operation, the

. second brush set is. set in the operative posie tion and stops when it reaches the first contact of its associated bank contact group.

pares .and the test relay P1. The magnet M1 re- The restoration of the brush carrier and the brush selector to normal, at the close of a talking connection, is effected by. the uniform further downward motion of the switching member until the brush selector reaches its lowest position. The slide then operates the compressed air device and the switch is restored to normal scribed manner.

The switching operations will now be de-' scribed in detail.

1. The operation-0f the line finder S1 9 On lifting the receiver at the calling sub scribers station No. 123, a current flows through the calling subscribers line group and the associated calling relay R, at the ex change, responds. Relay R excites relay A:

Positive, relay A, right'inner contact of relayR, resistance W2, negative.

-Relay Aexciteswith its inner contact,a relay U, which by operating the rotary magnet I) of a distributor V, causes a free line finder to be selected. At the same time the relay-A connects with its outer contact, the

test relay P of the distributor V to the positive pole. As soon as the lower switch arm .of the distributor meets a free line finder,

the following circuit is closed:

Positive, right outer contact of relay A, relay P, switch arm on the distributor V, contact 012 of a line finder S1, relay'Cl, neg ative.

The relays P and C1 respondto this current. Relay P, by opening its outer contact,

in the aforedestops the distributor V, and, by closing its inner contact, excites the magnet N1, which uncouples the brush selector from the brush circuit for the magnet M1, and by closing its left outer contact and its right contact, prea test circuit for the group selector (1 leases the brush carrier havingresponded to the following circuit:

Positive, left middle contact of relay 01,-

contact g1, left outer contact of relay P1,

interrupter contact z'l, magnet M1, negative.

Through the interrupter contact ii the circuit for the magnet M1 is so interrupted that the escapement movedby it never engages with the locking wheel teeth." As soon as the brush d of the line finder makes contact with the tens line (2) to which positive pole is applied by relay R, relay Z is excited:

Positive, relay A, right inner contact of relay R, line 2, brush-d, left outer contact of the relay C1, relay Z, negative.

By changing over its contact, relay Z-.in-

terrupts the excitation ofthe magnet N1.

which lets its armature drop back and couple the brush selector to the brush carrier. Since the brush carrier, up to the deenergization of the magnet N1, has travelled a distance of two switching steps, the brush set of the carrier of the line finder. RelayQCl closes a second tens group is then set in the opera-' tive position for the selection of the individual line in the second tens group. When the brush c1 ofthe second brush set engages with the contact of the calling subscriber, av

circuit arises for the test relay Pl as follows:

Positive, right contact of relay C1, both windings of relay Pl, brush 01, test line, right outer contact of the relay R, relay T, negative.

With this circuit the relays T and P1 are energized. Relay T, by openingits left contact, opensthe circuit of relay R and, by closing, its right contact, connects itself to the test line. Relay Pl, by opening its leftouter contact, opens the circuit of the magnet Ml and, by opening its left inner contact, opens the circuit of the relays C1 and P, the contact 012 having been opened when switching member commenced its falling movement. The

disconnection of the magnet M1 results in the immediate stopping of the line finder on the calling line. Relay P deenergizes and releases the distributor V for further calls. The slow acting relay C1 falls off somewhat later. In the meantime the relay P1, by closing its right contacts, has extended the talking line to the relay A2 of the group selector S2. Relay A2 responds over the subs-cribers line, and, with its outer left contact, excites the slow-acting relay V2. Relay V2, by its left outer contact, short-circuits the right winding of the test relay P1, whereby the calling subscribers line is blocked agalnst further calls.

2. Operation of the group selector S2 The relay V2. operated by the current impulse relay A2, excites, by closing its inner contact, a further slow-acting relay U2 as follows:

Positive, inner contact of the relay V2, con-,

tact e21, relay U2, negative.

Relay U2, by closing its left contact, excites the magnet N2, which effects the uncoupling of the brush selector, and, by changing over its right contact, prepares a circuit for the magnet M2 for operation by numerical current impulses.

Since the subscriber No. 321 .is wanted, the calling subscriber interrupts the line circuit three times so that relay A2 falls off three times. On each falling off of the relay A2, the magnet M2 is excited. Positive, right inner contact of the relay A2, right inner contact of relay U2, magnet M2, negative.

The brush carrier falls three switching steps. On the first step the contacts 021 and 622 are changed over. 021 interrupts the exciting circuit of the slow-acting relay U2 which/however, remains energized during these three releases of the relay A2 by a circuit extending through the left inner contact of relay A2 and its own left contact. After thereto,

these impulses have been sent the relay U2 slowly falls off. Relay U2, by opening its left contact, deenergizes the magnet N2, whereby the brush selector, after having set the third brush set in the operative position, is coupled with the brush carrier.

The right contact of therelay U2 closes, for the further selection, the following local circuit for the magnet M2:

I Positive, right contact of /the relay U2, contacts g2 and 622, right contact of the relay P2, interrupter i2, magnet M2, negative.

The magnet- M2 responds and releases the brush carrier with the brush selector coupled and is excited by the interrupter 712 in such a way that the escapengent pawl never engages with the teeth of thelocking wheel and thus the brush carrier and brush selector continue the downward movement with uniform motion. Assoon as the brush 02 of the group selector reaches the contacts of a free connector, the relays P2 (Fig. 15) and C3 (Fig. 16) are energized:

Positive, both windings of the relay P2, brush 02, test line contact 634 ofconnector S3, relay C3, negative.

Relay P2 by opening its right contact interrupts the circuit of the magnet M2. The group selector is thereby stopped. Relay P2 furthershort-circuits, with its left inner contact, its left winding, so that the connector is blocked. At the same time relay P2, by closing its left outer contacts, extends the talking line to the connector S3.

51. Operation of the connector 83 When the group selector is extended to the connector, relay A3 is energized:

Positive, right'windin of the relay A3, b-branch of the connecting line, brush 52 in the group selector, middle left contact of the relay P2, outer right contact of the relay A2, choke coil Dr, outer left contact of the relay P2, brush a2, a-Branch of the connecting line, left winding of relay A3, negative.

Relay A3 and the relay G3, already mentioned, together close the following circuit for the slow-acting relay V3:

Positive, outer contact of the relay C3, contact 631, right contact of relay A3, relay V 3, negative.

Relay V3 responds and excites the coupling magnet N3 and the slow-acting relay U3. Circuit for the magnet N3:

Positive, outer contact .of the relay V3, contact e32, magnet N3, negative.

Circuit for the relay U3:

Positive, outer. contact of relay C3, inner contact of relay V3, relay U3, negative.

Relay U3, by closing its outer contact, prepares a circuit for the magnet M3 for its operation by numerical impulses Toselect the desired number, the calling subscriber interrupts his line loop twice. On

pulses when relay A3 opens the right contact left contact of the relay U3, magnet M3,

negative.

Magnet M3 lets the brush carrier fall two switching steps. After the second step, the second brush set is in the operative position.

On the first switching step, the contacts 031 to 034 are changed over. Contact 031 interrupts the energizing circuit of the relay V3; but this relay is kept energized during the sending of the impulses, through the right contact of the relay A3, left inner contact of the relay U3, and the left outer contact of the relay C3, until after the transmission of imfor a longer period. 'Relay V3, on de-energization, opens the circuit of the coupling magnet N3, which up till now has remained energized, after the opening of the contact 032, through its own contact and the right contact of the relay V3. Magnet N3, on its deenergization, liberates the brush selector for its subsequent motion.

The calling subscriber, further selection, now interruptshis line loop once, the armatures of the relays A2 and A3 again fall-off and send an impulse, as previously, to the release magnet M3. The brush carrier now makes, together with the brush selector, a further switching step. The 0perative second brush set thus contacts with the called subscribers line.

Relay A3, on its last deenergization, energizes the relay V3:

Positive, outer contact of the relay C3, left inner contact of the relay U3, right contact of relay A3, relay V3, negative.

Relay V3 temporarily operates again,

therefore, on the last switching step and, with its inner contact, holds the relay U3 excited after its exciting circuit has been interrupted by the brush selector moving out of the normal position and opening contact f3.

The relays V3 and U3 successively fall off slowly after the last switching step.

on deenergizing, relay V3 closes, Whilst relay U3 is still excited, the following testing circuit over the selected line:

Positive, outer contact of the relay C3, right contact'of the relay U3, right contact of 'the relay V3, both windings of the test relay P3, contact of the relay Y, brush c3, test line, test relay T of the called subscriber, negative.

If the called subscriber is free, then the relays P3 and T are energized. Relay T disconnects the calling relay R" of the subscriber. Relay P3, by its left contact, shortcircuits its right winding and thereby renders the called subscribers line engaged. Also relay P3, with its two inner right 6011- for the purpose of tacts, connects the automatic calling signal to the called subscribers line as follows:

Positive, contact 0 of periodical interrupter right inner contact of the relay P3, brush a3, line loop of the subscriber No. 321, brush b3, outer right contact of relay P3, leftwinding of .relay Q, negative.

Alternating current is automatically sent, in definite time intervals, over this circuit to the bell of thecalled subscribers station. Relay Q does not respond to alternating current since its right winding is short-circuited.

Only when thecal-led subscriber answers does direct current flow through this circuit. The relay Q, then responds and, with its left contacts, extends the called subscribers line to the relay Y. Relay Y opens, with its contact, the short-circuit of the right winding of the relay Q so that this winding is also energized. Relay Q, with its right inner contact, shortcircuits the left windin of the relay P3, up to then energized, and thereby takes over the blocking of the called subscribers line in place of the relay P3 which, on account of the, short-circuiting, deenergizes and interrupts the alarm circuit.

The 'desired'connection is then completed.

4. Restoration of the selector is effected by inserting its release magnet M in the circuit of the interrupter when the callcontact, opens the circuit of the relay V2 which falls off and, with its outer contact opens the circuit of the relays P1 and T and, with its inner contact, opens the circuit of the relays P2 and C3. These relays are thus deenergized and their armatures fall ofl.

Relay P1 of the line finder closes, for the operation magnet M1, the following circuit: Positive, contacts 011 and g1, left outer contact of relay P1, interrupter i1, magnet M1, negative.

The magnet M1 is energized by interrupted current impulses, so that the line finder falls until the brush selector on reaching its lowest position, opens'the contact 71 and thus opens the circuit of the magnet M1. The brush carrier and brush selector are now raised to the normal position, the latter havingioperated the compressed air device.

elay P2 of the group selector closes, for the operation magnet M2, the circuit:

Positive, right contact of the relay U2,

contacts g2 and 622, right contact of the relay The magnet M2. operates like M1, until the brush selector on reaching its lowest position, opens the contact 92, and thus the circuit of the magnet M2, and operates the compressed air device.

Relay C3 of the connector, with its outer contact, opens the circuits of the relays V3,

P2, interrupter 2'2, magnet M2, negative.

U3 and P3 so that these drop their armatures provided they were still energized and close or prepare the following circuit for the release magnet M3.

Positive, outer left contact of the relay U3,

contacts 3 and 033, outer right contact of the relay P3, outer right contact of relay Q, interrupter 1'3, magnet M3, negative.

T his circuit is only closed when therelay Q is deenergized. The relay Q is, as indicated, energized when the called subscriber is at the apparatus. Consequently, after a conversation, the restoration of the connector is, in given cases, delayed until the called subscriber also hangs up the receiver and thus d-eenergized the relays Y andQ, The circuit for the magnet M3 acts as in the case of M2. and M1. l/V hen the brush selector reaches its lowest position it opens the contact 5 3 and operates the compressed air device.

Finally, it may be mentioned, that the production of the desired step-by-step or uniform motion of the switching member is not limited to the use of a double acting locking member (escapement paw-l). Fig. 18 shows a construction with only a'sim ple locking pawl secured to the armature of the magnet M, in combination with a circuit arrangement which provides a modification of the diagram for the group selector shown in Fig. 15. For the group selecting operation, which is'eliected by numerical impulses, a special relay X is provided which, during the excitation of the relays U2 and A2, is also excited, and, during the transmission of impulses through relay A2, allows its armature to t'allofl" quickly after each of the same have been sent. Thus the magnet- M receives periodical current impulses, so limited that. the locking pawl, before the next switching position has been reached, again returns into the locking position. After the changeover to the selection of the free connector, relay U2 then deenergizes, magnet M: is still remaining energized through the contact of relay U2, contact 2, already closed on the first switching step, contact 2 and the contact of the relay P2, and completely releases the switching member until, on its finding a free connector, relay P2 opens the circuit. The switching member remains in this position until. at the end of the conversation, the relay P2 deenergizes and againencrgizes the magnet M. The switching member. then continues to fall until contact 2 is opened when it reaches its lowest position. I

I claim x 1. A switching device for automatic telephone systems comprising a contact field with a plurality of groups of contacts, a movable switching member having a plurality of sets of brushes cooperating with said groups of contacts, means for making operative one set of brushes in accordance with a,

predetermined group of contacts, a constant force acting individually-on said movable the contacts of said contact field, means for locking the-switching member against the action of said force, means for releasing the lock-ing means and causing a movement until the operative brush set reaches the desired contacts and means for returning the switching member to initial position in a continuous movement at the end of a conversation.

2. A switching device for automatic telephone systems comprising a contact field with a plurality of groups-of contacts, a movable switching member having a plurality of sets of. brushes cooperating with said groups of contacts, means for making operative one set of brushes in accordance with a predetermined group of contacts, a constantly acting driving force acting individuallyon said movable switching member to move the same along the contacts of the contact field, a pawl mechanism for locking the switching member against the action of said force, means for releasing the locking means and causing a movement until the operative brush set reaches the desired contacts, and means for returning the switching member to its initial position in a continuous movement at the end of a conversation.

8. A switching device for automatic telephone systems comprising a contact field with a plurality of groups of contacts, a movable switching member having aplurality of sets of brushes cooperating with said groups of contacts, means for making operative one set of brushes in accordance with a predetermined group of contacts, a constant driving force acting individually on said movable switching member to move the same along the contacts of the contact field, a. pawl mechanism for locking the switching member against the action of said force, another pawl mechanism-for releasing the lock and for performing a movement until the operative brush set reaches the desired contact, and means for returning the switching member to its initial position in a continuous movement at the end of breaking of connection. 4. A switching device for automatic telephone systems comprising a contact field with a plurality of groups of contacts, a movable switching member having a plurality of sets of brushes cooperating with said groups of contacts, means for making operative one set of brushes in accordance with a prede termined group of contacts, a. constantly acting driving force acting individually on said movable switching member to move the same along the contacts of the contact field, a pawl mechanism for locking the switching member against the action of said force and for releasing it to movement until the desired contact/is reached by said operative set of brushes, and means for returning the switchswitching member to move the same along tion.

ing member to its initial position by a continuous movement at the end of the conver- Y sation. r 5. A switching device for automatic telephone systems comprising a contact field with v a plurality of groups of contacts, a movable switching member having a plurality of sets of brushes cooperating with said groups of contacts, means for making operative one set of brushes in accordance witha predetermined group of contacts, a constantly acting driving force acting individually on said movable switching member to move the same along the contacts of the said field, a pawl mechanism for locking the switching mem ber against the action of said force and for releasing the switching member to movement; said pawl mechanism embodying a two-armed escapement and a magnet controlling the escapement so as upon energi zation and de-energization to free the-switching member for movement for one half of the distance of two contacts of the field and then stop the same, and means for returning the switching member to its initial posi- 6. A switching device for automatic telephone systems comprising a contact field with a plurality of groups of contacts, a movable switching member having a plurality of sets of brushes cooperating with said groups of contacts, means for making operative one set of brushes in accordance with a predetermined group of contacts, a constantly acting driving force'acting on said movable switching member to move the same along the contacts of said field, a pawl mechanism for locking the over a plurality'of switching memberagainst the action of said force and for releasing said member to movement; said pawl mechanism embodying a two-armed escapement and a magnet controlling the escapement, an impulse transmitter for controlling the magnet dependent on the movement of the switching member for creating an oscillating movement of the escapement so as to retire the'pawl from looking .osition before the switching member reaches 1t, means for bringing into circuit'the impulse transmitter so as to, cause an uninterrupted movement of the switching member contacts, means for disconnecting the impulse transmitter so as to cause a stopping of the switchingmember, and means for returning the switch-ing member to its initial position.

7. A switching device for automatic tele phone systems comprising a contact field with a pluralityot groups of contacts, a movable switching member having a plurality of sets of brushes cooperating with said groups of contacts, means for making operative one set of brushes in accordance with a predetermined group of contacts, a constantly acting driving. force operable individually on said switching member to move the same along the along the contacts of the field, a pawl mechacontacts of the field, a pawl mechanism for locking the switching member against the action of said force and for releasing said mem-- ber to movement; said pawl mechanism embodying a one-armed operating pawl, an electromagnet for controlling said operating pawl, and means for energizing the electromagnet so as upon energizationto move the pawl to free the switching member for continuous movement along a plurality of contacts, means for tie-energizing the electromagnet so as to lock the switching member, and means for returning the switching member to its initial position.

8. A switching device for automatic telephone systems comprising a contact field with a plurality of grou s of contacts, a movable switching member aving a plurality of sets of brushes cooperating with said groups of contacts, means for making operative one set of brushes in accordance with a predeter-' mined group of-contacts, a constantly acting driving force operable individually on the switching member so as tomove the same nism for locking the switching member against the action of said force and for releasing the switching member to movement; said pawl mechanism embodying a one-armed operating pawl, an electromagnetfor controlling said operating pawl, means for energizing the electromagnet so as upon energization to move the pawl to free the switching member for continuous movement along a plurality of contacts, means the electromagnet so as to lock the switching member, a transmitter for numerical impulses, means controlled by said transmitter for creating a to-and-fro movement'of the pawl, temporarily controlling the to-and-fro movement of the pawl in such manner that the pawl returns to the lock-ing position before the switching member reaches said position, and means for returning the switching member to its initial 1 position.

9. A'switching device for automatic telephone systems comprising a contact field with a plurality of groups of contacts, a movable switching member having a plurality of 1 sets of brushes cooperating with said groups of contacts, means for making operative one set of brushes in accordance with a predetermined groupof contacts, a constantly acting driving force operating individually on said 1 movable switching member so as to move the same along the cont-acts of said field, a pawl mechanism for locking the switching member against the action-of said force and for releasing said member to movement. means for 1 operating the pawl mechanism to allow movem nt of the switching member until a position corresponding with the predetermined set of contacts is. reached, means for making operative a set of brushes corresponding to 1 for de-energizing 106 acting switching means said set of contacts, means for actuating the pawl mechanism again to permit a continued movement of the switching member until the desired contact is reached. by the set of brushes made operative, and means for returning the switching member to its initial position.

10, A line finder in automatic telephone systems including a contact field having a plurality of contact groups, comprising a movable switching member having a plurality of sets of brushes cooperable with said groups of contacts, means for making operative one set of brushes corresponding to a predetermined roup of contacts, a constantly operative driving force acting individually on said switching member so as to move the same along the contacts of said field, a pawl T mechanism for locking the switching mcmher against the action of said force and for releasing the same again to movement, means dependent on the contacts of the field for controlling the pawl mechanism to allow a continuous movement of the switching member until the desired group of contacts is reached by the corresponding set of brushes,means also dependent on the contacts of the field for controlling the pawl mechanism to creating a continued and continuous movement of the switching member until the desired contact is reached within the desired contact group by a set of brushes made operative, and means for returning the switching member to its initial positio Y 11. A selector for automatic telephone systems including a contact field having a plurality of groups of contacts, comprising a movable switching member carryin a plurality of sets of brushes and cooperating with said groups of contacts, means for making operative one set of brushes corresponding L the contacts of the to a predetermined group of contacts, a constantly' acting driving force operating individually on said switching member to move the same along the contacts of said field, a pawl mechanism for locking the switching member against the action of said force and for allowing movement thereof respectively, a numerical impulse transmitter, means dependent on said transmitter for controlling the pawl mechanism to create a step-by-step movement of the switching member until the desired group of contacts is reached by the corresponding brush set, meansdependent on contact field for controlling the pawl mechanism to create a further continuous movementof the switching memher until the contact connected with an idle line of the desired contact group is reached by the set of brushes made operative, and means for returningthe switching member'to its initial position. Y

12. A connector in automatic telephone systems including a contact field having a plurality of groups-of Fontacts, comprising a movable switching member carrying a number of sets of brushes cooperating with said groups of contacts, means for making operative one set of brushes corresponding to a predetermined group of contacts, a constantly acting driving force operating individually on said switchingimember to move the same along the contacts of said field, a pawl mechanism for locking the switching member against the action of said force and forpermitting movement thereof respectively, a numerical impulse transmitter, means dependent on said transmitterv for controlling the pawl mechanism to create a step-by-step movement of the switching member until the desired group of contacts is reached by the corresponding set of brushes and until the desired contact within such group is reached by the set of brushes made operative, and means for returning the switching member to initial position. .13. In an automatic eluding a contact field having a plurality of groups of contacts and a row of contacts corresponding to said groups of contacts, a line finder comprising a movable switching member carrying a plurality of sets of brushes cooperating with contacts within said groups and a set of brushes cooperating with said row of contacts, a constantly acting drivtelcphone system ining force operating individually on said movable switching member to move the same along the contacts of said field, means for selecting one set of brushes during a partial movement of the switching member until a predetermined group of contacts is reached, means for making operative the selected set of brushes at the end of such partial movement of the'switching member, a pawl mechanism for. locking the member against the action of said force and for permitting movement thereof respectively, switching means in connection with the set of brushes cooperating with said row of contacts and dependent on said row for controlling the pawl mechanism to create a continuous movement of the-switching member until the desired group of contacts is reached by the corresponding set of brushes, means dependent on the contacts of the field for controlling said pawl mechanism to create a continued and continuous movement of the switching M. A switching device for automatic telephone systems havin plurality of groups 0? contacts, compris ng a movable switching member embodyin two parts movable one against the other in the direction of the switch movement, one of said parts being constructed as abrush support carrying a plurality of sets of brushes co-.

a contact field with a 

